What troubleshooting step should be taken if a boiler's water level is too low?

In the situation where a boiler's water level is too low, inspecting the feedwater supply for blockages is an essential troubleshooting step. This is because a low water level can often be attributed to insufficient water being supplied to the boiler. If there are blockages in the feedwater lines or supply, it prevents water from entering the boiler, which can lead to overheating and possible damage.

By ensuring that the feedwater supply is open and functioning appropriately, you can restore the necessary water level, which is vital for safe and efficient boiler operation. Maintaining the right water level prevents problems such as dry firing, which can cause significant damage to the boiler components and potentially lead to a hazardous situation.

The other options may not sufficiently address the immediate issue of low water level. For instance, increasing fuel supply or turning off the steam output does not resolve the fundamental problem of insufficient water. Changing the thermostat does not directly impact the water level management either. Therefore, focusing on the feedwater supply is the most effective first step in troubleshooting low water conditions in a boiler system.